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Pilot error caused a twin helicopter crash in Argentina that killed three French sports stars, five crew members and two Argentine pilots filming a reality TV show in March, investigators said Thursday.

The two helicopters collided on March 9 while filming the French television series "Dropped," killing renowned yachtswoman Florence Arthaud, Olympic champion swimmer Camille Muffat, Olympic boxer Alexis Vastine and all seven others on board.

After a lengthy inquiry, Argentina's aviation investigations unit, JIAAC, found in a nearly 50-page report that the pilots -- who were both experienced -- failed to realize how close together their Eurocopters were flying.

"The triggering factor of the accident was, according to the information obtained during the investigation and its analysis, the pilots' lack of perception of the closeness or the deficit in the separation between their respective aircraft," it said.

"This lack of perception led to the air collision of the aircraft without attempting any evasive or defensive maneuvers."

Amateur video taken from the ground showed the helicopters flying extremely close, their rotors clipping and both aircraft plummeting.

One of the helicopters was in the process of circling the other when the accident ocurred -- a common maneuver in such TV shoots.

One of the pilots may have been blinded by the sun, said the report.

Investigators found no evidence of mechanical failure or technical problems.

Distractions' to blame

The report said the show's production schedule had been delayed that fateful day, and speculated that time constraints and the pressures of a TV shoot could have contributed to the accident, even though both pilots were experienced.

"It is plausible to hypothesize that the photographer's need of recording the images could have influenced the pilot's distributive vision control, or even caused distractions," it said.

But, it added, "the lack of protected data recording devices or cockpit voice recorders does not allow to draw any decisive conclusions regarding potential distractions that the pilots may have experienced."

Investigators also found the provincial government-owned helicopters were not normally supposed to be used for a private film shoot.

And they said there were "deficiencies" in the planning of the flights.

"Dropped," which was to air on French channel TF1 but was immediately canceled, featured sports stars taken blindfolded into rugged environments and given 72 hours to get to a place where they could charge a cell phone.

Arthaud, 57, was considered one of the best sailors in the world, conquering what had been a male-dominated sport.

Muffat, 25, won three medals at the 2012 London Olympics, including gold in the 400-meter freestyle. Vastine, 28, won bronze at the Beijing Olympics in 2008.

The crash also killed five French TV crew members, as well as the Argentine pilots.

Other participants on the show included Olympic champion swimmer Alain Bernard, figure skater Philippe Candeloro and cycling legend Jeannie Longo.

They described rushing to the crash site from the spot where they had been awaiting their turn to fly to the next shoot, then watching helplessly as the helicopters burned on the scrubland of Argentina's remote, mountainous northwest.